Example aspects herein relate to an integrated wheel disconnect system for a vehicle, and more particularly, to a system which selectively connects or disconnects driving and driven components of the wheel disconnect system to render selected wheels passive or driven.
Four wheel drive vehicles often have either front or rear wheels that have selectively driven or non-driven modes which operate by selectively engaging or disengaging the wheels from an associated drive train. In these four wheel drive systems, typically, a transfer case, coupled to the vehicle transmission, is designed such that it can be engaged or disengaged from the drive train. The engagement of the transfer case with the drive train selectively supplies power to a set of wheels. Although efficiencies can be obtained by solely disengaging the transfer case when not needed, it is known in the art that disengaging the wheels from the drive train improves driving efficiencies dramatically.
Where a transfer case is selectively disengaged from the drive train and the associated wheel set remains engaged, losses may result from the wheels “back driving” the system and having to overcome the rotational moment of inertia of half shafts, axle carrier assemblies, pinion shafts, and associated frictional losses in bearings, seals and gears. Therefore, it is desirable to have a wheel disconnect system that works in concert with the transfer case, engaging when the transfer case is engaged and disengaging when the transfer case disengages. It should be recognized that such wheel end disconnect systems may be used on either the front or rear wheels, depending upon which wheel set has the primary drive function.
Prior art wheel end disconnect systems utilize a vacuum system in order to disengage the wheel spindle from the drivetrain. Typically, such systems include a spindle supported by bearings in a support coupled to a suspension member, having an outer end portion adapted to mount a wheel thereon, and an inner extending portion, disposed towards the center of the vehicle with a radially extending flange that has engaging elements formed, generally on an outer diameter, of the flange. A drive element adapted to rotate under power is mounted adjacent the flange, with an engaging element or clutch slideably mounted thereon, such that it can be selectively moved into and out of engagement with the spindle flange of the wheel. The engaging element or clutch requires an axial force, as previously described, provided by a vacuum system, to disengage from the wheel assembly. Generally, a spring is also provided, that urges the engaging clutch back into engagement once the vacuum has been removed.
An inherent limitation of such a system is that a separate vacuum system must be provided, with associated difficulties in scaling the system properly to provide constant negative pressure.